When a driving a vehicle, an emergency may arise in which the driver of the vehicle is no longer able to operate the vehicle due to his/her health condition such as sudden symptom occurrence or worsening of an illness. Japanese Patent Application No. 2015-207264 discloses a device that stops a vehicle automatically by detecting occurrence of such an emergency. In this device, the driver pushes a predetermined emergency stop switch when he/she intends to stop the vehicle (stop intention). The device detects the driver's stop intention by the pushing of the emergency stop switch, and also determines that the driver is in a state where he/she is unable to drive (hereinafter referred to as “unable-to-drive state”) when a predetermined driving operation such as an acceleration operation is not performed for a predetermined time or longer.
Then, the device determines whether an emergency has occurred according to both of presence or absence of a stop intention and presence or absence of the unable-to-drive state. Upon detection of both of the stop intention and the unable-to-drive state, the device determines that an emergency has occurred and automatically stops the vehicle at a predetermined deceleration speed. Upon detection of only one of the stop intention and the unable-to-drive state, the device determines that it is highly probable that an emergency has occurred and stops the vehicle at a lower deceleration speed than the aforementioned predetermined deceleration speed. Thus, the device prevents an immediate automatic stop of the vehicle due to erroneous detection of an emergency when no emergency has occurred, and also prevents continuance of normal travel due to erroneous detection that no emergency has occurred when an emergency has occurred. Japanese Patent Application No. 2015-207264 also discloses that the device cancels automatic stop control, when it detects that the driver has performed a predetermined driving operation for a predetermined time while performing automatic stop control.
The above conventional stop control device is capable of appropriately detecting an emergency and stopping a vehicle safely. However, since it is difficult for the driver to accurately sense the time period of a driving operation such as an acceleration operation, the driver may have difficulty in knowing whether it has been determined to activate the automatic stop function or whether it has been determined to cancel the function in the device, and how to initiate a desired operation (e.g., activation or cancellation of the function). As a result, an unexpected start of automatic stop control caused by an unintentionally long no driving time, or the inability of appropriately determining the required amount of driving operation time for canceling automatic stop control after the start of the control may confuse the driver. Such confusion is more likely to happen when the driver has the aforementioned sudden or urgent problem concerning his/her health condition, and an erroneous operation by the confused driver may lead to a secondary disaster.